In daily life, people often need to exchange image, video, text and other types of files between, for example, a personal computer (PC) and a mobile phone. To facilitate this interaction between the PC and the mobile phone, a communication channel has to be first established between the PC and the mobile phone. In practice, the communication channel between the PC and the mobile phone is usually implemented using a wired connection (e.g., a USB cable). However, a wired connection has limitations that reduce the easiness of user operations.